Many underwater optical system for communications, gated viewing, surveillance, and bottom mapping require efficient high peak power pulsed transmitters in the blue-green spectral region (i.e. 4600A to 5100A). This requirement is dictated by the physical fact that transmittance of power in ocean waters is most efficient when the source of optical power emits within the aforementioned spectral region, known as the "ocean window". In other words, minimum attenuation and maximum efficiency can be attained by employing light energy sources which emit principally within the spectral range of the so-called ocean window.
For example, pulsed lasers in the form of frequency doubled neodymium systems emitting principally at the 5300A spectral region have been used relatively commonly as a source of optical energy for underwater systems. Unfortunately, however, the attenuation coefficient for optical energy at the 5300A wavelength is approximately twice as large as the minimum value for deep ocean waters which can be realized within the ocean window spectral range of 4600A to 5100A.
More recently, pulsed dye lasers have been under development for use as a source of optical energy in underwater optical systems. One most important aspect of the performance of selected dye lasers in their capability of being tunable to provide a principal portion of their emitted output of optical energy at wavelengths within the blue-green ocean window spectral region of 4600A to 5100A where the attenuation in ocean waters is at its minimum value.
In the employment of such dye lasers in underwater optical systems, to avail more fully of their advantageous use one of the limitations which must be overcome is the inefficient transfer of energy from prior art, currently available flash lamp excitation sources to the absorption spectral region of the dye laser material. Current and prior state of the art dye laser flash lamp excitation sources include lamps filled with xenon gas to provide a pulsed emission of a quasi-continuous nature resembling that of a black body. Unfortunately, however, the emitted optical energy of such xenon lamps is a poor match with the absorption spectral region of many dye lasers materials; that is, the principal peak energy outputs of such xenon lamp dye laser excitation sources occurred in regions outside the absorption spectral band between 3600A and 4300A.
The use of many other inert gases in addition to xenon have been explored as a potential flash lamp dye excitation sources but unfortunately none is presently known to provide any truly significant improvement over the prior art xenon flash lamps in terms of producing a principal amount of peak light energy output within the absorption spectral region of many dye laser materials and as defined hereinbefore.
Accordingly, it is highly desirable that an improved flash lamp for dye laser excitation be devised and that the radiation from such improved flash lamps include at least the three following characteristics:
1. Enhanced emission must occur principally within the desired wavelength spectral region. PA1 2. The emission must be greater than that from prior art flash lamps excited under similar conditions. PA1 3. The peak emitted power must be sufficiently large to have practical utility in the excitation of dye laser materials in practical optical systems.